cs 440 lecture 2

cs 440 lecture 2 - CS 440: Database Management Systems...

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Unformatted text preview: CS 440: Database Management Systems Review of Relational Algebra z How to design a language to query a relational database? Relational algebra z Procedural, explain how results are obtained Relational calculus z Declarative, no need to specify the steps Review of Relational Algebra z Queries consist of a collection of operators z Every operator accepts one or two relation instances as input and return a relation instance as output z Combining these operators can form more complex queries Review of Relational Algebra z Basic operators SELECT ( ), PROJECT ( ), RENAME ( ) UNION ( ), INTERSECTION ( ) , MINUS (-) CROSS PRODUCT ( ) JOIN ( ), DIVISION ( ) z EQUIJOIN, NATURAL JOIN (*) U I >< Review of Relational Algebra z Extended Generalized to include projection of functions Aggregate functions and grouping F Recursive closure operation OUTER JOIN z LEFT OUTER JOIN ( ) z RIGHT OUTER JOIN ( ) z FULL OUTER JOIN ( ) OUTER UNION >< >< >< Review of Relational Algebra z Selection z Projection ) ( 5 . 3 Students GPA > ) ( , , Students GPA SName SID Review of Relational Algebra z Display the ID, Name, and GPA of students with a GPA > 3.5 Review of Relational Algebra z Display the ID, Name, and GPA of students with a GPA > 3.5 ) ( 5 . 3 , , Students GPA GPA SName SID > Review of Relational Algebra z Union of two sets of relation instances S R John 12345 Jean 54321 R Mike 12405 Kathy 43109 S Review of Relational Algebra z Union of two sets of relation instances John 12345 Jean 54321 R Mike 12405 Kathy 43109 S Mike 12405 Kathy 43109 John 12345 Jean 54321 S R S R Review of Relational Algebra z Union of two sets of relation instances John 12345 Jean 54321 Mike 12405 R Mike 12405 Kathy 43109 S S R Review of Relational Algebra z Union of two sets of relation instances John 12345 Jean 54321 Mike 12405 R Mike 12405 Kathy 43109 S Mike 12405 Kathy 43109 John 12345 Jean 54321 S R S R Review of Relational Algebra z Union of two sets of relation instances John 12345 Jean 54321 R Mike TX Kathy OR S S R Review of Relational Algebra z Union of two sets of relation instances John 12345 Jean 54321 R Mike TX Kathy OR S Mike 12405 Kathy 43109 John TX Jean OR S R S R Review of Relational Algebra z Union of two sets of relation instances John 12345 Jean 54321 R Mike TX Kathy OR S Mike 12405 Kathy 43109 John TX Jean OR S R Review of Relational Algebra z Union-compatibility Same number of fields Same domain for every corresponding field John 12345 Jean 54321 R Mike TX Kathy OR S Mike 12405 Kathy 43109 John TX Jean OR S R Review of Relational Algebra z Intersection S R John 12345 Jean 54321 Mike 12405 R Mike 12405 Kathy 43109 S Relational Algebra z Intersection John 12345 Jean 54321 Mike 12405 R Mike 12405 Kathy 43109 S Mike 12405 S R S R Relational Algebra z Intersection needs to respect union- compatibility, too....
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cs 440 lecture 2 - CS 440: Database Management Systems...

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